Transformer



S. E. JOHANNESEN.

TRANSFORMER.

APPLl-C 1916- ].,323Q77Q. Patented Dec. 2,1919.

Inventor:

Svend Edohannesen His Attorney.

UNI ED STATE-s PATENT: OFFICE.

SVENDE. OHANNESEN, OF PITTSFIELD, MASSACHUSETTS, ASSIGNOR TO GENERAL ELECTRIC COMPANY, CORPORATION OF NEW YORK.

To all whom it may concern:

Be it known that I, SVEND E. Jorrnrrrm- SEN, a citizen of the United States, residing at Pittsfield, county of Berkshire, State of Massachusetts, have invented certain new and useful Improvements in Transformers, of which the following is a specification.

My invention relates to transformers provided with taps whereby the voltage impressed on'the load circuit may be varied; it relates particularly to transformers without moving parts for supplying constant current series circuits, or circuits adapted to receive substantially constant current and 15" in which the devices constituting the. load are connected in series. One object of my invention is to provide a method of changing the voltage impressed on a circuit by such devices as transformers without changing the per cent. reactance of such devices.v Another object is to provide a trans former in which the number of active turns may b varied without materially changing 'its per cent. reactance. Other objects of pressed in per cent. of theopen circuit secondary voltage, depends materially the decrease in secondary voltage with increase of current, the current on short circuit, and

the effect of the transformer in determining the power factor of its primary c rcuit. 1

The reactance of a transformer as transformers are generally constructed, while not absolutely uniformly distributed through out the windings, changes substantially as the square ofthe number of turns; thus if the number of active turns of a given transformer are doubled, the 'reactance is increased about four times, and if the number of active turns are decreased the reactance is decreased in a corresponding manner. The percent. reactance of such a transformer,

TRANSFORMER.

Specification of Letters Patent.

Patented'Dec. 2, 1919.

Application filed August 24, 1916. Serial No. 116,636.

of course changes each time the reactance.

is changed, for the open circuit secondary voltage changes something like directly,

In general in transformers embodying my v nvention, I divide the secondary Winding into two portions to be connected in series, one of which 1s in closer inductive relation to the primary winding than the other and hence of lower reactance, and I preferably provide for changing the number of turns in each group Whenever the-number of active turns is to be changed. The method of operation of my invention may be understood therefrom. This method comprises making each change of voltage by changing the number of secondary turns by Varying both the number of active secondary turns in poorer inductive relation to the primary and the number of active secondary turns in closer inductive relation to the primary windings. Under some conditions it will be sufficient, however, in making each change in voltage to change only the number of secondary turns in closer inductive relation to the primary windings as will appear hereinafter, the active secondary turns in poorer inductive relation to the primary windings being unchanged. By employing my invention the number of taps which may be applied to any transformer is subject to considerably less limitations than heretofore.

vention, and in the claims, I refer to primary and secondary windings. It will be understood, however, that I do this mainly for the sake of clearness and simplicity of description, and that in practice the windings I refer to as primary windings may, indeedfsupply the load, the so-called sec In the above and hereinafter in the de-, taildescription of embodiments of my inof this specification.

ondary windings receiving. energy from the supply lines.

My invention, as before indicated, is particularly applicable to those stationary transformers used to supply series circuits from constant potential sources and which depend upon a considerable value of reactance to maintain thecurrent supplied at something like a constant value irrespective of some changes in the load. Such transformers are not capable of taking care of extreme changes in load without corresponding changes in the number of 'active' turns, and heretofore such changes in turns have. involved considerable changes in the per cent. reactance of the device with corresponding changes in the regulation, the possible current on short circuit and the power factor. By employing my invention, however, it is possible to provide a stationary transformer of the desired high reactance in which the number of active turns may be varied as desired over a wide range unaccompanied by such detrimental effects; it is possible therefore to provide a single transformer which by lmeans of taps is adapted to supply either relatively great or small loads "and intermediat loads, all with substantially the same operating characteristics sofar as they are affected by the reactance of the transformer. i

The accompanying drawings to which reference is hereinafter made, form a part Figure 1 is a diagrammatic illustration of a preferred form of transformer embodying my invention. Fig. 2 is a development of the windings of the transformer of Fig. 1, certain means for making the connections being diagrammatically illustrated.

The transformer illustrated in these drawings is of high reactance; it is designed particularly for supplying series circuits and is required to suppl more or less constant current although itself supplied with substantially constant potential. 9 While my invention is particularly applicable to this type of apparatus, some consideration will show that it is not limited thereto but it is applicable to transformers of other types and for other purposes.

In practice the transformer I employ is substantially like that diagrammatically illustrated in Fig. 1. The core 3 is of the center leg type, all the windings being assembled on the middle leg and the return for the magnetic flux being provided by external legs as indicated. The main secondary windings 4 comprise a plurality-of layers placed one above another; I have indicated the plurality of la ers by the use of light and heavy lines. aps, as 5 and 6,

are provided inthese windings as {may be necessary; 7 and 8 are the terminals of these.

windings. The primary windings 9 are shunt 11 is provided between the primary and auxiliary secondary windings on the one hand and the main secondary windings on the other; air gaps are left between the magnetic shunt and the core. The magnetic shunt enables me to reduce somewhat the length of the core. The auxiliary secondary windings are preferablydividedinto two portions 12 and 13 electrically separated from each other. Each portion is provided with such taps and terminals, 1621, as may be necessary; as hereinafter indicated the tap, or taps, of the smaller of these two portions divides this portion into relatively small parts. In Fig. 2 the windings of the transformer of Fig. 1 are developed, and for a further understanding of my invention reference may be had to Fig. 2 wherein the windings bear the same reference characters disposed in the same way as in Fig. 1, it'being understood in considering Fig. 2 that considerable magnetic leakage is provided for between the primary windin s 9 and the main secondary windings i. This figure also diagrammatically 1 illustrates means 25 for connectingthe taps and terminals of the secondary windings to the lines 26 and to each other in various arrangements. 4

It must be understood that each turn of the windings of the drawings does not necessarily represent one turn in practice, but each turn of the drawing may represent a plurality of turns of a transformer constructed or operated in accordance with my invention; for the purpose of this specifica tion however, the relative numbers of turns between the various taps and terminals of the secondary winding may be regarded as something as indicated by the drawings.

The use of theterms main secondary windings? and auxiliary secondary windings is not intended to indicate the relative numbers of turns in the main and auxiliary secondary windings. Both the numbers of l turns between the various taps and terminals cording to my invention, preferably the number of activeturns in both the main and auxiliary secondary windings are varied. Suppose, for example,

the load circuit for some particular load is attached to the tap 5-and the terminal 8 of the main secondary windings 4, the auxiliary secondary windings being inactive and not employed for this degree of full load. The load on the secondary circuit may be varied within certain limits without a material change in the current therein, for by reason of the high reactance of the transformer due to the location of the main secondary windings 4 with respect to theprimary windings 9, the regulation ispoor' and the voltage impressed on the load circuit does not change proportionally to the load. This is the general plan of the action of certain simple so-called constant current transformers without moving parts. The range of action, that is the range throughout which 'the load may-be varied without encountering an undesirable change in current, is however small and strictly limited unless some additional provisions are made for handling the major changes. Suppose now that the load on the transformer of Fig. 1, becomes or is about to become so great that the value of the current change is undesirable, that is, the current is established or is about to be established at an undesirably low value; in that case the number of activeturns of the secondary windings must be increased to such an extent that the current through the load is again approximately the desired value. These increased active turns are preferably obtained partly by adding active turns to the main secondary windings at and partly by adding active turns to the auxiliary secondary windings 10; for example by connecting the load circuit to the terminal 8 of the main seconda windings 4 and to the tap 17 of the auxi iary'secondary'windings 10, the terminal 7 being connected to the tap or terminal 18. If now the transformer has been properly so designed, this change in the number of active turns is secured Without a' change in the per cent. reactance, and hence also without a change in the effect of the transformer on the power factor of the circuit supplying the primary windings,

without changing the possible value ofthe current on short circuit .and without affecting the regulation of the transformer. This may be regarded as due to the fact that the total reactance of the transformer has two components of different values, one determined by the main secondary windings t andthe other: by the auxiliary secondary windings 10. Both-of these components are affected by the change in the number of active turns in such proportions that their resultant with respect to the voltage at the line terminals (that is the percent; reactance) remains unchanged. When the transformer is essentially .of high-reactance as in the Case illustrated, the number of turns varied in the so-called main secondary windings will be greaterin each instance than the J number of turns varied in the auxiliary secondary windings at least where the per cent. reactance is to be held about constant.

If, however, it is found that the correc tion for the change in load is not quite right, another. part, or other parts, of the second ary windings may be added or subtracted until the proper correction is made. For this purpose'the taps (in the auxiliary secondary windings especially) divide the windings into unequal numbers or parts. F or example, if the original correction is not far wrong, the part of the auxiliary sec ondary windings between: the tap 20 ,and the terminal 21 (which is very small) may be connected in series with the load circuit, either bucking or boosting the remainder of the active secondary turns as the conditions require; in the former case the voltage impressed on the lOad circuit is reduced and the per cent. reactance increased, and in the latter case the load voltage is increased and the per cent. reactance reduced. If the'proper, correction is still to be found for this particular load-,other slight changes may be made as by connecting the load circuit to the terminals 8 and 16 and connecting one or more parts of the auxiliary secondary "windings 10 between the tap 19' and the terminal 21, in opposition between the tap 18 and the terminal 7 Thus by providing the auxiliary secondary windings with a number of taps preferably unequally distributed along its length, and preferably also providing for the connection of parts of those wlndings in oppositlon to other parts thereof as by the division of the auxiliary secondary windings 10 into separated parts, not only maythe voltage and reactance be adjusted for considerable changes in load, but also the adjustment may be very accurately made in 'each case irrespective of the unavoidable errors in the design and construction of the transformer.

If, in the first case, instead of desiring to maintain the per cent. reactance at the Same value as before, the original change in the number of active turns, some increase in the per cent. reactance had been desired with the same increase" in' voltage, thisless turns between thertaps l and-18 of theauxiliary secondary windings .10. Likewise, the per cent. reactance might evenhave been decreased with the increase in the number of active turns by. providing a few more turnsv between the taps 17 and 18 of the aux il iary secondary windings 10 and a few less between the tap 5 and terminal. 7 of the main secondary windings 4. Thus it will be observed, by my invention the effect of I the number of active turns in both the main and auxiliary secondary windings. Thus the first step (the load before the change being connected between 8 and 5) may be by the connection of the load circuit leads to the terminal 8 and to the tap or terminal 18, the taps 6 and 17 being connected to.- gether. The portion of the auxiliary secondary windings between the taps 17 and 18 buck or oppose the main secondary windings and the effect is the same .as though some auxiliary secondary windings had previously been connected in series boosting with the main secondary and the number of active turns of said auxiliary secondary had been decreased with the decrease in active turns in the main secondary. As in the previous case where the load and voltage were increased, more or less minor adjustments maybe made by connecting a few more turns in series with the main secondary windings, either bucking or boosting the voltage induced therein, and likewise the per cent. reactance may be varied as desired or held substantially constant.

Thus far the detailed description hasrelated to a complete form of my invention, and where this form is employed a single apparatus may serve loads subject to changes throughout a considerable range and the reactance may be very closely controlled. Where the range of load changes is less extensive, and particularly where the er cent. reactance may permissibly be su ject to some slight changes with change in voltage,

the simplified form of my invention suggested before may be employed. According to this form of my invention each en-- tire change in voltage is secured by changing only the number of active turns in the auxiliary secondary windings, the number of turns in the main secondary windin remaining the same. Thus, referring again to Fig. 2 and contemplating only a oad of three values, the load at intermediate value may be connected to the terminals 7 and 8 of the main secondary windings; the highest load which the transformer is adapted.

to supply may be connected to the terminals 8 and 16, the taps18 and 19- being connected together and the terminals 7 and 21 being connected together, the entire main and auxiliary secondary windings being connected in series and boosting; the lowest load of the transformer may be connected to the terminals 8 and 21, the terminals 7 and '16being connected together and the taps 18 and 19 being connected together,

the main and auxiliary secondary windings being connected in series and bucking each other. Since the taps illustrated are not employed inthis form of my invention, they may be omitted from apparatus designed particularly for following this simplified form of my invention. It will be observed that when the auxiliary secondary windings are connected in series boosting with the main secondary windings and the voltage is raised thereby, the per cent. reactance tends to remain at more nearly its original value than heretofore and may even assume a lower value than originally; also when these two windings are connected in series bucking, the voltage is lowered without the usual great decrease in per cent. reactance, for the lower voltage has been obtained by adding active bucking turns (rather than subtracting turns) and the decrease in reactance is due to propulsion of current through the auxiliary secondary windings in opposition to the voltage induced therein.

my invention and the best modes I have contemplated for applying this principle, other modifications will occur to those skilled in this art and I aim in the appended claims to cover all modifications which do not involve a departure from the spirit and scope of my invention.

WVhat I claim as new, and desire to secure by Letters Patent of the United States, is

1. The method of varying the voltage impressed on a circuit by means of inductively related primary and secondary windings so wound on a closed magnetiecore that certain secondary turns are in poorer inductive relation to the prima winding than other secondary turns, whic consists in securing the desired variation by varyingboth the number of active secondary turns in poorer inductive relation tothe primary and the number of active secondary turns in closer inductive relation to the primary in such pressed on a circuit by means of inductively related primary and secondary windings so wound on a closed magnetic core'that certain secondary turns are in poorer inductive relation to the primary winding than other secondary turns, which consists in securing the desired variation b varying both the number of active secon ary turns in poorer inductive relation to t e primary and the number of active secondary turns'in closer inductive relation to the primary, the num- .ber of turns varied in poorer inductive relation being greater in each instance than the number of turns varied in closer inductive relation to the primary.

3. The method of varying the voltage impressed on a circuit by means of inductively related primary and secondary windmgs so wound on a closed magnetic core'that cer.

and a predetermined desired per cent. re'

actance, the two secondary groups being connected in series.v 1

4. The method of varying the voltage impressed on a circuit by means of inductively related primary and secondary windings so wound on a closed magnetic core that certain secondary turns are in poorer induc- -tive relation to the primary winding than other secondary turns which consists in securing each desired variation by varying both the number of active secondary turns in poorer inductive relation to the primary and the number of active secondary turns in closer inductive relation to the primary, the number ofturns varied in poorer inductive relation being greater in each instance than 80 the number of turns varied in closer inductive relation to the primary, and the two secondary groupsbeing connected in series. -5. The method of varying the. voltage impressed on a circuit by means of inductively related primary and secondary windings wherein certain secondary turns are in poorer inductive relation to the primary winding than other secondary turns, which consists in securing each desired variation 40 by so varying the number of active secondary turns in poorer inductive relation to the primary and so varying" the number of active secondary turns in closer inductive relation to the primary that the desired change in voltage is secured and the total per cent. re-

actance of the inductively related windings is substantially unchanged.

6. A transformer comprising primary windings, main secondary'windings. so in- .ductively related thereto as to provide for large magnetic leakage between the two, auxiliary secondary windings in closer inductive relation to the primary winding and -means for connecting portions of said auxiliary and-main secondary windings in series bucking or boosting.

7. A transformer comprising primary windings, main secondary windlngs inductivel related thereto, auxiliary secondary win ings in closer inductive relationto the primary windings and electrically separate from said main secondary windings, taps in the main secondary windings and taps di-.

, viding the auxiliary secondary windings into portions-of unequal numbers of turns,

the taps and terminals of said main and auxiliary secondary windings being brought out for interconnection and connection to the line in various arrangements.

8. A transformer comprising primary windings, main secondary windings inductively related thereto, auxiliary secondary windings in closer inductive relation'to the primary windings, the auxiliary secondary windings being divided into two electrically separate major and minor parts, taps in the main secondary windings, taps in the major part of the auxiliary secondary winding, taps dividing the minor part of the auxiliary secondary winding into portions of unequal, relatively small, numbers of turns, and means for connecting portions ofjsaidmain and auxiliary secondary windings in series.

, 9. A transformer comprising primary windings, main secondary windings inductively related thereto, auxiliary secondary windings in closer inductive relation to the primary windings and means for connecting portions of said main and auxiliary windings in bucking or boosting relations.

10. A- transformer comprising primary windings, main secondary windings inductively related thereto, auxiliary secondary windings in closer inductive relation to the primary windings, a coreof magnetic material interlinking said windings, and means for connecting a major portion of said main secondary windings alone to the line and for connecting said main and auxiliary secondary windings in series to the line.

11. A transformer comprising primary windings, main secondary windings inductively related thereto; auxiliary secondary windings in closer inductive relation to the primary windings, a core of magnetic material interlinking said windings, and means for connectin said main secondary windingsalone to the line and for connecting said main and auxiliary secondary windings in series bucking or boosting to the line.

12. A transformer comprising primary. windings, main secondary windings so inductively related thereto as to provide for large magnetic leakage between the two, auxiliary secondary windings in closer inductive relation to thb primary windings,

a core of magnetic material inter-linking said. windings, and means for connecting a major portion Of said main secondary windings alone to the line and, for connecting said main and auxiliary secondary windings in series to the line.

a, 13. The method of varying the voltage impressed on a circuit by means of relatively stationary inductively related primary and secon ary windingsso wound on a closed magnetic core-that certain second ary turns are in poorer inductive relation to the primary winding than other secondary turns, which consists in securing each de sired variation by varying the number of I curing each desired variation by varying active secondary turns in closer inductive such a number of active secondary turns in relation to the primary windings. such closer inductive relation to the primary 14. The method of varying the voltage windings that the desired change in voltage impressed on a circuit by means of inducis secured and the total per cent. reactance is 15 tively related primary andlsecondary wind-' changed as desired. 7 ings so wound on a closed magnetic core that In witness whereof, I have hereunto set certain secondary turns are in poorer inducmy hand this 18th day of August, 1916. tive relation to the primary winding than 10 other secondary turns, which consists in se- SVEND E. J OHANNESEN. 

